Increased ER and oxidative stress in chm^ru848 zebrafish. The expression of ER (A) and oxidative stress markers (B) were analysed in wt and chm fish at 5 dpf using RT-qPCR. ER and oxidative stress markers are differentially expressed in chm fish, compared to wt. Data expressed as mean ± SEM from n = 3 (denoted by black dots for wt and black squares for chm fish). * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001, **** p ≤ 0.0001.

Increased ER and oxidative stress in CHM^Y42X patient fibroblasts. (A) The expression of ER stress markers was analysed in WT and CHM fibroblasts using RT-qPCR. Data expressed as mean ± SEM from n = 3. (B) Representative western blot showing reduced BIP protein expression in CHM fibroblasts. (C) Quantification of BIP protein from n = 3 blots. (D) The expression of oxidative stress markers was analysed using RT-qPCR. (E) No significant difference in the SOD enzyme activity between WT and CHM fibroblasts. Data expressed as mean ± SEM from n = 3 (denoted by black dots for wt and black squares for chm fish). * p ≤ 0.05, ** p ≤ 0.01.

Analysis of ER stress in TUDCA-treated chm^ru848 fish and CHM^Y42X cells. Fish were treated with 20 µM of TUDCA or DMSO at 3 dpf and collected at 5 dpf for (A) retinal histology and (B) the RT-qPCR analysis of the ER stress markers atf6, bip and atf4. TUDCA reduces the expression of ER stress markers. (C) Cells were treated with either 100 µM of TUDCA or DMSO and the expression of the ER stress markers CHOP and BIP was analysed using RT-qPCR. Data are expressed as mean ± SEM from n = 3. * p ≤ 0.05, ** p ≤ 0.01, *** < p ≤ 0.001 **** p ≤ 0.0001. Scale bar (50 μm), shown in wt corresponds to all images in panel.

Analysis of ER stress in taurine-treated chm^ru848 fish and CHM^Y42X cells. Fish were treated with 100 mM of taurine at 3 dpf and collected at 5 dpf for (A) retinal histology and RT-qPCR analysis of (B) the ER stress markers atf6, bip and atf4 and (C) the oxidative stress markers txn, cat and sod3a. (D) Cells were treated with 100 mM of taurine and the expression of SOD2 and ER stress markers CHOP and BIP was analysed using RT-qPCR. Data are expressed as mean ± SEM from n = 3. * p ≤ 0.05, *** < p ≤ 0.001. Scale bar (50 μm), shown in wt corresponds to all images in panel.

Analysis of oxidative stress in NACA-treated chm^ru848 fish and CHM^Y42X cells. Fish were treated with 200 µg/mL of NACA at 10 hpf and collected at 5 dpf for (A) retinal histology and (B) RT-qPCR analysis of the oxidative stress markers txn, cat and sod3a. (C) Cells were treated with either 1 mM of NACA, and the expression of SOD2 and the ER stress markers CHOP and BIP was analysed using RT-qPCR. Data are expressed as mean ± SEM from n = 3. * p ≤ 0.05, ** p ≤ 0.01, *** < p ≤ 0.001. Scale bar (50 μm), shown in wt corresponds to all images in panel.

Analysis of melanin in L-dopa-treated chm^ru848 fish. Fish were treated with 1 mM of L-dopa at 3 dpf and collected at 5 dpf for (A) retinal histology, (B) total melanin quantification and (C) RT-qPCR analysis of the oxidative stress markers txn, sod3a and cat. Data are expressed as mean ± SEM from n = 3. * p ≤ 0.05, ** p ≤ 0.01, **** p ≤ 0.0001. Scale bar (50 μm), shown in wt corresponds to all images in panel.